package u1;

import static java.lang.System.*;
import static u1.Util.*;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Scanner;

/**
 * Takes adjacency list on standard in. Takes the name of a node list file as
 * its first argument. The node list should be node (page) numbers delimited by
 * whitespace. Produces an adjacency list for the subgraph induced by the node
 * list on standard out.
 */
public class Subgraph {
  public static void main(String[] args) throws FileNotFoundException {
    if (args.length != 1) {
      err.println("See comments for usage.");
      exit(-1);
    }

    String startFile = args[0];

    /*
     * Scan start nodes.
     */
    trace("Reading start nodes from %s...", startFile);
    Scanner startScanner = new Scanner(new File(startFile));
    final HashSet<Integer> start = new HashSet<Integer>(PAGES_MAX);
    while (startScanner.hasNextInt()) {
      start.add(startScanner.nextInt());
    }
    startScanner.close();
    trace("Got %d start nodes.", start.size());

    final AdjWriter writer = new AdjWriter(out);
    final HashSet<Integer> subgraphTargets = new HashSet<Integer>();
    AdjReader reader = new AdjReader() {
      @Override
      public void readLinks(Integer source, Collection<Integer> targets) {
        if (start.contains(source)) {
          subgraphTargets.clear();
          for (Integer target : targets) {
            if (start.contains(target))
              subgraphTargets.add(target);
          }
          if (subgraphTargets.size() > 0) {
            writer.write(source, subgraphTargets);
          }
        }
      }
    };
    reader.read(in);
    trace("Read %d pages and %d links.", reader.getPageIndex(), reader
        .getLinkCount());
    trace("Wrote %d pages and %d links.", writer.getPageCount(), writer
        .getLinkCount());
  }
}
/*
* Copyright (c) 2009 John Lees-Miller
* 
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
* 
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/

